The present invention relates to a method for adjusting height of a magnetic head, such as a double azimuth type magnetic head which is assembled in a video tape recorder, for example.
The video tape recorder is provided with a cylinder head 52, around an outer peripheral face of which a video tape 50 supported by means of guide pins 51, 51 slidably runs, as shown in FIG. 4. The video tape 50 slidably runs in a state where it is wound around the cylinder head 52 at a determined inclination angle and along a determined angular range with respect to the cylinder head 52. A pair of double azimuth type magnetic heads (hereinafter referred to simply as xe2x80x9cmagnetic headxe2x80x9d) 53 are mounted at an equal interval on the cylinder head 52 with their one portions exposed from the outer peripheral face of the cylinder head. Each of the magnetic heads 53 includes a printed board 54, a pair of base plates 55 which are assembled to one side of the printed board 54 in a cantilever manner, and head chips 56 which are respectively attached to distal end portions of these base plates 55, as shown in FIGS. 5 and 6.
The magnetic head 53 is assembled to the cylinder head 52 in such a manner that a sliding face 56a of the head chip 56 in which a magnetic gap G is formed (see FIG. 7D) is exposed outward from the outer peripheral face of the cylinder head 52. The magnetic head 53 precisely records and reproduces, in a rotating state of the cylinder head 52, recorded image information, audio information, and so on by helically scanning the video tape 50 which is slidably running around the outer peripheral face of the cylinder head at high speed. For this reason, it is necessary for the magnetic head 53 to locate the magnetic gap G of the head chip 56 precisely in a scope of some micron with respect to a recording track of the video tape 50, as shown in FIG. 6.
By the way, the magnetic head 53 varies in height because of variation in thickness of the head chips 56 due to slicing accuracy when the head chip 56 is manufactured, or pasting accuracy when this head chip 56 is pasted to the base plate 55, and an adjusting operation of the height is required. In a related method for adjusting the height as disclosed in Japanese Patent Publication No. 8-55319A, for example, the height of the head chip 56 has been adjusted by varying flatness of the base plate 55 with respect to a reference plane.
After the above described adjusting operation has been conducted, a sliding face 56a of the head chip 56 in the magnetic head 53 is polished in order to give a favorable touch with the video tape 50. This polishing process is conducted by mounting the magnetic head 53 on a polishing jig in a cylindrical shape like the cylinder head 52 and by driving a wrapping tape to run. The wrapping tape slidably runs at a determined inclination angle and a winding angle in a determined range, in the same manner as the video tape 50, thereby polishing the sliding face 56a of the head chip 56 so as to give a desired curvature.
The height of the magnetic head 53 has been adjusted by bending and deforming the base plate 55 at a desired angle by means of a press member 62 and a push-up member 63 in a state where a base part of the base plate 55 is held between a holding table 60 and a press board 61, as specifically shown in FIG. 7A. The base plate 55 of the magnetic head 53 is bent and deformed by pushing up the push-up member 63 from below in a state where a projected portion of the base plate 55 is pressed from above by the press member 62.
However, in such a related method for adjusting the height, the distal end portion of the base plate 55 is bent and deformed in an arcuate shape around a pressing position of the press member 62, as shown in FIG. 7B. As a result, the sliding face 56a of the head chip 56 will not be retained in parallel to the reference track plane. Accordingly, when the above described polishing process is applied to the sliding face 56a of the head chip 56, an apex of a curvature r in a direction of thickness in an area near the track is displaced by an amount of xcex94x with respect to a center of the gap G, as shown in FIG. 7C.
For this reason, a center P of magnetic interference fringes generated on the sliding face 56a of the head chip 56 is deviated from the center O of the magnetic gap G, as shown in FIG. 7D. Such magnetic head 53 is inferior in recording and reproducing property for the image information and the audio information, because tape touch will be worsened when the magnetic head has been assembled to the cylinder head 52, even though the above described height adjustment has been conducted.
In view of the above, an object of the invention is to provide a method for adjusting height of a magnetic head in which recording and reproducing property with higher accuracy can be obtained by simply conducting the height adjustment, while maintaining the sliding face of the head chip in parallel to a reference track plane.
In order to achieve the above object, according to the present invention, there is provided a method of adjusting a height of a head chip, which is attached to one end portion of a base plate to constitute a magnetic head, with respect to a reference plane of the base plate, comprising the steps of:
placing a face of the base plate which is to be the reference plane onto a first plane face of a die member; and
punching a punch member onto a predetermined portion of the base plate toward a diagonal direction with respect to the reference plane such that a portion of the base member on which the head chip is attached is shearing-deformed by a predetermined amount in the punching direction.
Preferably, the predetermined amount is set within a plastic deformable range of the base plate.
Preferably, the die member is provided with a second plane face extending orthogonally to the first plane face. The second plane face, the predetermined portion of the base plate and a shearing blade face of the punch member are arranged on an identical line.
Preferably, the deforming direction of the base plate is parallel with a sliding face of the head chip, which is to be slid on a recording medium.
In the above configurations, a shearing deformation process is conducted on the sliding face of the head chip while keeping a diagonal attitude thereof with respect to the reference plane. Accordingly, adjustment of the height is conducted in a state where the sliding face of the head chip and a reference track plane of the recording medium are kept in parallel to each other. Therefore, when the polishing process is applied to the sliding face of the head chip, the center of the curvature of the sliding face and the center of the magnetic gap are substantially aligned, to give a favorable tape touch, whereby a magnetic head which can carry out recording and reproduction with high accuracy can be manufactured. Further, the height adjustment with high precision can be simply performed, and necessity of assembling the magnetic head to a cylinder head employing various spacers will be eliminated. Remarkable improvement of working efficiency will be thus attained.